/*
 * Copyright (c) 2011-2018, Novyon Events
 * 
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 * 
 * - Redistributions of source code must retain the above copyright notice, this
 * list of conditions and the following disclaimer.
 * 
 * - Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 * 
 * @author Anthyon
 */
package com.jme3.terrain.noise.filter;

import com.jme3.terrain.noise.Basis;
import java.nio.FloatBuffer;

public class HydraulicErodeFilter extends AbstractFilter {

    private float Kr;
    private float Ks;
    private float Ke;
    private float Kc;
    private float T;

    public void setKc(float kc) {
        this.Kc = kc;
    }

    public void setKe(float ke) {
        this.Ke = ke;
    }

    public void setKr(float kr) {
        this.Kr = kr;
    }

    public void setKs(float ks) {
        this.Ks = ks;
    }

    public void setSedimentMap(Basis sedimentMap) {
            // not implemented
    }

    public void setT(float t) {
        this.T = t;
    }

    public void setWaterMap(Basis waterMap) {
            // not implemented
    }

    @Override
    public int getMargin(int size, int margin) {
        return super.getMargin(size, margin) + 1;
    }

    @Override
    public FloatBuffer filter(float sx, float sy, float base, FloatBuffer buffer, int workSize) {
        float[] ga = buffer.array();
        // float[] wa = this.waterMap.getBuffer(sx, sy, base, workSize).array();
        // float[] sa = this.sedimentMap.getBuffer(sx, sy, base,
        // workSize).array();
        float[] wt = new float[workSize * workSize];
        float[] st = new float[workSize * workSize];

        int[] idxrel = { -workSize - 1, -workSize + 1, workSize - 1, workSize + 1 };

        // step 1. water arrives and step 2. captures material
        for (int y = 0; y < workSize; y++) {
            for (int x = 0; x < workSize; x++) {
                int idx = y * workSize + x;
                float wtemp = this.Kr; // * wa[idx];
                float stemp = this.Ks; // * sa[idx];
                if (wtemp > 0) {
                    wt[idx] += wtemp;
                    if (stemp > 0) {
                        ga[idx] -= stemp * wt[idx];
                        st[idx] += stemp * wt[idx];
                    }
                }

                // step 3. water is transported to its neighbours
                float a = ga[idx] + wt[idx];
                // float[] aj = new float[idxrel.length];
                float amax = 0;
                int amaxidx = -1;
                float ac = 0;
                float dtotal = 0;

                for (int j = 0; j < idxrel.length; j++) {
                    if (idx + idxrel[j] > 0 && idx + idxrel[j] < workSize) {
                        float at = ga[idx + idxrel[j]] + wt[idx + idxrel[j]];
                        if (a - at > a - amax) {
                            dtotal += at;
                            amax = at;
                            amaxidx = j;
                            ac++;
                        }
                    }
                }

                float aa = (dtotal + a) / (ac + 1);
                // for (int j = 0; j < idxrel.length; j++) {
                // if (idx + idxrel[j] > 0 && idx + idxrel[j] < workSize && a -
                // aj[j] > 0) {
                if (amaxidx > -1) {
                    float dwj = Math.min(wt[idx], a - aa) * (a - amax) / dtotal;
                    float dsj = st[idx] * dwj / wt[idx];
                    wt[idx] -= dwj;
                    st[idx] -= dsj;
                    wt[idx + idxrel[amaxidx]] += dwj;
                    st[idx + idxrel[amaxidx]] += dsj;
                }
                // }

                // step 4. water evaporates and deposits material
                wt[idx] = wt[idx] * (1 - this.Ke);
                if (wt[idx] < this.T) {
                    wt[idx] = 0;
                }
                float smax = this.Kc * wt[idx];
                if (st[idx] > smax) {
                    ga[idx] += st[idx] - smax;
                    st[idx] -= st[idx] - smax;
                }
            }
        }

        return buffer;
    }

}
